Ok, so after investigating further, i realized that when you make a downloadable build for your game, then there are several problems which can occur, to create an alternate build in WebGL (i'm using Unity):
1 - The folder destination of your save files is different, it is a specific spot in WebGL online server, and I/O commands need to change as well with another set of specific instructions;
2 - Seems that the Addressable files will be another big problem as well... on WegGL they won't be found with current settings;
3 - I also heard that save files cannot be bigger than 10 Mb (playerprefs seems that they even have a lower limit of 1 Mb, but i use JSON for saves), at the current state one save file of my game gets a size of 5-8 Mb, i fear that i might escale to 10+ Mb according to how long the run keeps going (and i still have to implement multi save slots!)
4 - Debugging errors during WebGL build execution (which would make anything feasible to fix) is pointless: no Unity console actual feedback, it has no access to the editor and this is disruptive for me.
(any other issue? I don't know, they are more than enough already, but if you know other issues as well, feel free to add them to my list)
For such reasons at the current state i decided to postpone a plan to make a WebGL version, which is quite unfortunate on itch...
If any other dev around here is seeing this, could you please share some useful info that might allow me to get past this huge barrier? I doubt i'm the first dev that ever had to convert a downloadable build into a WebGL build, although my game features several layers of complexity, as it is